"With 1,300 lots, we had to rejig the internet program [application] to take it.

"It will be certainly the biggest Holden-themed auction in South Australia that I've ever known."

Mr Skipworth's daughters employed Mr Bennett a year ago to sort through the material.

"It was a bit mind-blowing when I realised how much stuff that they had," Mr Bennett said.

"The family were taking me around. The more they took me around, the more shocked I was."

Bennetts had to sort the vast collection into pallet lots rather than individual pieces, which still took three days to auction.

The auction house's owner said just about all the 120 cars listed for sale needed restoration, but the return on investment was well worth it.

"We had a 10 per cent jump in the value of old Holdens as soon as the factory closed a couple of years ago, and ever since we've had a jump of at least 10-15 per cent a year in the value of these ones. And they keep going up," Mr Bennett said.